HTML5 is a language for structuring and presenting content for
the World Wide Web, and is a core technology of the Internet originally proposed by Opera Software.
It is the fifth revision of the HTML standard
(created in 1990 and standardized as HTML4 as of 1997)[2]
and as of March 2012
is still under development. Its core aims have been to improve the
language with support for the latest multimedia while keeping it easily
readable by humans and consistently understood by computers and devices (web
browsers, parsers, etc.). HTML5 is intended to subsume not
only HTML 4, but XHTML 1 and DOM Level 2 HTML as well.[update]
Following its immediate predecessors HTML 4.01 and XHTML 1.1, HTML5
is a response to the observation that the HTML and XHTML in common use
on the World Wide Web are a mixture of features introduced by various
specifications, along with those introduced by software products such as
web browsers, those established by common practice, and the many syntax error in existing web documents.
It is also an attempt to define a single markup language that can be written in either HTML or
XHTML syntax. It includes detailed processing models to encourage more
interoperable implementations; it extends, improves and rationalises the
markup available for documents, and introduces markup and application
programming interfaces (APIs) for complex web applications.
For the same reasons, HTML5 is also a potential candidate for
cross-platform mobile applications. Many features of HTML5 have been
built with the consideration of being able to run on low-powered devices
such as smartphones and tablets. In December 2011 research firm
Strategy Analytics forecast sales of HTML5 compatible phones will top 1
billion in 2013.
In particular, HTML5 adds many new syntactical features. These
include the new
<video>, <audio> and <canvas> elements,
as well as the integration of Scalable Vector Graphics (SVG) content that replaces the
uses of generic <object> tags. These features are
designed to make it easy to include and handle multimedia
and graphical content on the web without
having to resort to proprietary plugins and APIs. Other new elements,
such as <section>, <article>, <header>
and <nav>, are designed to enrich the semantic content of documents. New attributes have been introduced for the same purpose,
while some elements and attributes have been removed. Some elements,
such as <a>, <cite> and <menu>
have been changed, redefined or standardized. The APIs and document object model
(DOM) are no longer afterthoughts, but are fundamental parts of the
HTML5 specification.
HTML5 also defines in some detail the required processing for invalid
documents so that syntax errors will be treated uniformly by all
conforming browsers and other user
agents.
Standardization process
The Mozilla Foundation and Opera Software presented a position paper at a World Wide
Web Consortium (W3C) workshop in June 2004, focusing on developing technologies that are backwards compatible with
existing browsers,
including an initial draft specification of Web Forms 2.0. The workshop
concluded with a vote, 8 for, 14 against, for continuing work on HTML.
Later that month, work based upon that position paper moved to the
newly formed Web Hypertext Application Technology Working Group
(WHATWG), and a second draft, Web Applications 1.0, was also announced.
The two specifications were later merged to form HTML5.
The HTML5 specification was adopted as the starting point of the work
of the new HTML working group of the W3C in 2007. This working group
published the First Public Working Draft of the specification on 22
January 2008.
Parts of HTML5 have been implemented in browsers despite the whole
specification not yet having reached final Recommendation status.
According to the original W3C timetable, it was estimated that HTML5
would reach W3C Recommendation by late 2010, after a Last Call in 2008.
However, the First Public Working Draft estimate was missed by eight
months, and Last Call was only reached in 2011.
On 14 February 2011, the W3C extended the charter of its HTML Working
Group with clear milestones for HTML5. In May 2011, the working group
advanced HTML5 to "Last Call", an invitation to communities inside and
outside W3C to confirm the technical soundness of the specification. The
W3C is developing a comprehensive test suite to achieve broad
interoperability for the full specification by 2014, which is now the
target date for Recommendation.
HTML5 introduces a number of new elements
and attributes that reflect typical usage on modern websites.
Some of them are semantic replacements for
common uses of generic block (
<div>)
and inline (<span>)
elements, for example <nav>
(website navigation block), <footer>
(usually referring to bottom of web page or to last lines of HTML
code), or <audio> and <video> instead of <object>.
Some deprecated elements from HTML 4.01 have been dropped, including purely
presentational elements such as <font>
and <center>, whose
effects are achieved using Cascading Style Sheets.
There is also a renewed emphasis on the importance of DOM
scripting (e.g., JavaScript) in Web behavior.
The HTML5 syntax is no longer based on SGML[dubious
] despite the similarity
of its markup. It has, however, been designed to be backward compatible
with common parsing of older versions of HTML. It comes with a new
introductory line that looks like an SGML document type
declaration,
<!DOCTYPE
html>, which triggers the standards-compliant rendering
mode. As of 5 January 2009, HTML5 also includes Web Forms 2.0, a
previously separate WHATWG specification.New APIs
In addition to specifying markup, HTML5 specifies scripting application
programming interfaces (APIs).[34]
Existing document object model
(DOM) interfaces are extended and de facto
features documented. There are also new APIs, such as:
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HTML5 alone cannot provide animation within web pages. Either JavaScript
or CSS3 is necessary for animating HTML elements.
Animation is also possible using JavaScript and HTML 4, and within
SVG elements through SMIL, although
browser support of the latter remains uneven as of 2011.
XHTML5
XHTML5 is the XML serialization of HTML5. XML documents must be
served with an XML Internet media type such as
application/xhtml+xml
or application/xml.
XHTML5 requires XML's strict, well-formed syntax. The choice between
HTML5 and XHTML5 boils down to the choice of a MIME/content type: the
media type one chooses determines what type of document should be used.[48]
In XHTML5 the HTML5 doctype html is
optional and may simply be omitted. HTML that has been written to conform to both the HTML and XHTML
specifications—and which will therefore produce the same DOM tree
whether parsed as HTML or XML—is termed "polyglot markup".Error handling
An HTML5 (text/html) browser will be flexible in handling incorrect syntax.
HTML5 is designed so that old browsers can safely ignore new HTML5
constructs.[citation needed]
In contrast to HTML 4.01, the HTML5 specification gives detailed rules
for lexing and parsing,
with the intent that different compliant browsers will produce the same
result in the case of incorrect syntax.[51]
Although HTML5 now defines a consistent behavior for "tag soup"
documents, those documents are not regarded as conforming to the HTML5
standard.[51]
The HTML5 logo
On 18 January 2011, the W3C introduced a logo to represent the use of
or interest in HTML5. Unlike other badges previously issued by the W3C,
it does not imply validity or conformance to a certain standard. As of 1
April 2011, this logo is official.
When initially presenting it to the public, the W3C announced the
HTML5 logo as a "general-purpose visual identity for a broad set of open
web technologies, including HTML5, CSS, SVG, WOFF, and others".Some web standard advocates, including The Web Standards Project,
criticised that definition of "HTML5" as an umbrella term, pointing out
the blurring of terminnlogy and the potential for miscommunication. days later, the W3C responded to community feedback and changed
the logo's definition, dropping the enumeration of related technologies. The W3C then said the logo "represents HTML5, the cornerstone for
modern Web applications".
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